Multi-colored plastic building product and its manufacture

ABSTRACT

A multi-colored cast plastic building product of uniformity and strength including a mass of polymeric material having distributed an suspended therein at least one smaller elongated continuous pattern of a different colored polymeric material in a predetermined reproducible three dimensional configuration and a manufacturing arrangement for producing the same so that the polymeric materials are substantially equally matched as the degree of polymerization at the time of being cast to give uniformity of all properties except color in the final product.

6 Sheets-Sheet 1 I N. L. HALL ETAL March 16, 1971 MULTI-COLORED PLASTICBUILDING PRODUCT AND ITS MANUFACTURE Filed July 24, 1969 INVENTORSNELSON LEE HALL DONALD HILLMAN SLOCUM BY- ATTORNEY l lll 5,

March 16, 1971 I I N. L. HALL ETAL.

MULTI-COLORED PLASTIC BUILDING PRODUCT AND ITS'MANUFACTURE Filed July24, 1969 6 Sheets-Sheet 2 F I G 2 ATTORNEY March 16, 1971 N. L. HALLETAL 3,570,056

MULTI-COLORED PLASTIC BUILDING PRODUCT AND ITS MANUFACTURE Filed July24, 1969 6 Sheets-Sheet 3 INVENTORS NELSON LEE HALL DONALD HILLMANSLOCUM ATTORNEY March '16, 1971 N HALL T L 3,570,056

MULTI-COLORED PLASTIC BUILDING PRODUCT AND ITS MANUFACTURE Filed July24, 1969 v e Sheets-Sheet 4 ZONE 11 26 zone I 20x5 111 INVENTORS A msouLEE HALL 5 DONALD mum sLocun ATTORNEY N. L. HALL ETAL March 16, 1971MULTI-COLOBED PLASTIC BUILDING PRODUCT AND ITS MANUFACTURE Filed July24, 19 69 6 Shets-Sheet e omw v innit M M w m U QM- N C R E O %0 W3 /m MW W E L A U m F & L wm E0 ND United States Patent 3,570,056MULTI-COLORED PLASTIC BUILDING PRODUCT AND ITS MANUFACTURE Nelson LeeHall, Williamsville, N.Y., and Donald Hillman Slocum, Moorestown, N.J.,assignors to E. I. du Pont de Nemours and Company, Wilmington, Del.

Filed July 24, 1969, Ser. No. 844,509 Int. Cl. 1829c 9/00; B291. 1/02,1/12 US. Cl. 184 8 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THEINVENTION This invention relates generally to the field of improvedmulti-colored cast slabs, sheets, and articles useful in the buildingarts and having a predetermined controlled appearance and structurepleasingly similar in many cases to natural stone such as marble. Alsoinvolved are improved apparatus and process arrangements by which theseproducts can be mass-produced commercially from certain polymericcompositions.

It is a general object of the invention to provide an improved buildingproduct with a predetermined appearance and structure, having highlyuniform properties except for color and preferably generally similar tonatural marble yet capable of controlled infinite variation and alsocapable of reproduction on a large commercial scale.

It is another general object to provide simple, economical, high speed,effective and reliable process and apparatus arrangements for commercialmanufacture of the improved product of the invention, preferably ofpolymeric materials such as poly (methyl methacrylate) filled withcalcium carbonate.

Other objects and advantages Will be apparent from the followingspecification, claims, and accompanying drawings.

PRIOR ART BACKGROUND OF THE INVENTION Multi-colored cast plasticarticles simulating stone such as natural marble, and the processes andapparatus for making them are known in the prior art. Examples of sucharticles, some of which are made by incorporating colored pigments inhighly filled resin bases are disclosed, together with theirmanufacturing arrangements to prior US. patents such as Nos. 1,120,632;1,638,109; 2,040,- 863; 2,280,488; 1,699,413; 1,845,457; 3,050,785;2,174,- 779; 3,422,175; 3,388,196; 2,477,170; and 3,396,067. It isbelieved that the closest prior art related to the present invention isrepresented by the above-identified related US. patent application to R.B. Duggins. In this item of prior art, a cast multi-colored sheetsimulating marble with a predetermined reproducible three dimensionalcolor pattern is described along with an arrangement for itsmanufacture. This sheet and its manufacture involved a relatively widevariation in time of curing or polymerizing compared with certainrecently developed more accurately controllable uniformly rapid cure, orpolymerization, systems especially adapted for highly filled polymers.With these more recent accurately predictable and accelerated 3,570,056Patented Mar. 16, 1971 "ice polymerization systems, and particularly athigher production rates, it has become of greater importance that thecast articles, which have a colored stream of polymeric materialdisposed throughout a base polymeric material of a different color, areproduced under carefully controlled conditions such that all materialshave substantially equally matched degrees of polymerization at the timeof casting so the final product materials will be uniform in allproperties except colors. Without this matching and uniformity inproperties cast articles of the type exemplified by the prior art havehad portions of unequal strength and sometimes develop undesirablewarpage during the exothermic polymerization reaction by which they areproduced. In order to produce these cast articles with better uniformityand strength and also handle satisfactorily the more recently developedrapid polymerizing materials, With their rapid heat generation and rapidincrease in viscosity it was necessary to provide the new and improvedprocess and apparatus arrangements described herein which possessfeatures for achieving the equally matched degrees of polymerizationthroughout the product being cast and for achieving rapid economicalhandling of the highly viscous thixotropic rapidly polymerizingmaterials used. The novel apparatus and process features also contributeto a wider degree of variability in the colored patterns which can beproduced and are believed to represent a valuable contribution to theart.

SUMMARY OF THE INVENTION Generally stated the objects of the inventionand the contribution to the art are achieved in the production of acastable flowable extruded colored stream of predetermined dimensions ofrapidly polymerizing thixotropic material throughout which isplastically distributed at least one continuous separately identifiablesmaller stream of rapidly polymerizing thixotropic material of adifferent color in a predetermined reproducible three dimensionalconfiguration with the viscosities, densities, and degrees ofpolymerization of said streams being substantially equally matched toprovide substantial uniformity of all properties except color throughoutthe final cast structure formed thereby.

Also involved in the achievement of the objects of the invention and thecontribution to the art is a manufacturing arrangement of means andprocess steps in which controlled quantities of rapidly polymerizablematerials are brought together, polymerization initiated, and thematerials intimately mixed in a first confined zone of high shear mixingaction, the mixed materials from the first zone are formed into firstand second streams of rapidly polymerizing material of controlledrelative sizes, one of said streams being conducted to a second zone ofhigh shear mixing action where it is intimately mixed with a contrastingcoloring material and then conducted to a third mixing zone of low intensity low shear mixing action and gently mixed with the other streamconducted there from the first high shear mixing zone. This low shearmixing action of the third zone progressively displaces the one streamwith the contrasting coloring material throughout the other stream in atleast one predetermined reproducible three dimensional configurationwhile substantially maintaining the continuity of the configurations ofthe one stream. The conditions, rates, dimensions and configurations ofthe streams, process, and apparatus are carefully estab lished,controlled, and coordinated so that, in addition to producing thereproducible pattern or configuration of the contrasting coloredmaterial, with the rapidly polymerizing combined streams still in afiowable castable condition at the casting location, the materials ofthe combined streams are substantially equally matched as to density,viscosity, and degree of polymerization to give 3 the desired uniformityof properties, excepting color, to the final product.

Other features and aspects of this general summary of the invention willappear hereinafter.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial longitudinal crosssectional view of an apparatus for producing cast articles embodyingprinciples of the invention with certain parts shown broken away for aclearer showing. The view of FIG. I is taken at line 1-1 of FIG. 3.

:FIG. 2 is a partial transverse cross sectional view of the apparatus ofFIG. 1 taken at line 2-2 of FIG. 3 with certain parts shown broken away.

FIG. 3 is a partial plan view of the apparatus of FIGS. 1 and 2 withcertain parts shown broken away for clearer showing.

FIG. 4 is an enlarged partial cross sectional view of the movable mixingand casting assembly of the apparatus shown in FIGS. 1, 2, and 3.

FIG. 5 is an enlarged end view of the extrusion orifice of the mixingand casting assembly taken at line 5-5 of FIG. 4.

FIG. 6 is a partial schematic plan view showing one version of thecontroller for programming casting in the mold assembly.

FIG. 7 is a block diagram illustrating the general manufacturing processarrangement.

FIGS. 8A, 8B, and 8C are enlarged partial longitudinal cross sectionalviews showing alternate forms of the final zone low shear mixingcomponent of the mixing and casting assembly shown in FIG. 5.

FIG. 8D is a partial elevational view of the component of FIG. 8C takenat line 8D-8D.

DETAILED DESCRIPTION OF THE INVENTION The improved high speed highthroughput process capable of continuously producing a uniformly strong,rigid, cast plastic structure useful in the building art and formed of afilled polymeric composition having pleasing multicolored structure andapparances resembling marble is illustrated in a block diagram in FIG.7, and generally comprises the following basic steps:

Bringing together in a first reaction zone (Zone I) having predetermineddimensions, and under controlled conditions, monomer and polymer sirups,fillers, base colored pigments, catalysts, promoters, and modifiers;subjecting these materials to a high intensity intimate thorough mixingaction under predetermined controlled conditions of a high shear mixing,temperature, and pressure to produce a homogeneous, uniformly colored,polymerizing mass; forming the thixotropic polymerizing mass into twofiowable streams of predetermined relative size conducting one of thestreams into at least one second confined zone (Zone II) havingpredetermined dimensions under controlled conditions of temperature andpressure while adding into Zone II at controlled rates at least oneseparate stream comprising coloring pigments to form a homogeneouscolored mass which differs from the base color of Zone I; subjectingthis mass in the second zone to a controlled high intensity, high order,high shear mixing action at predetermined controlled shear rates,temperatures and pressures, to intimately mix the colored pigments intothe polymerizing mass, conducting this differently colored mass in astream under predetermined controlled conditions of temperature andpressure, at predetermined flow rates from the second zone through aconduit of controlled length of predetermined size into a third zone(Zone III) having predetermined dimensions; while from Zone I,conducting the other stream from Zone I through a conduit ofpredetermined controlled length and size into Zone III; recombining thestreams from Zones I and II in Zone III under controlled conditions oftemperature, pressure, low order, low intensity, low shear mixing actionsimilar to fold blending to form separately identifiable distinct veinpatterns comprising at least one differently colored polymerizing streamprogressively displaced in the base colored stream of polymerizingingredients in a controlled predetermined general pattern of structure,the veins of polymerizing differently colored material having a degreeof polymerization substantially equal to the degree of polymerization ofthe base colored material and preferably substantially equal inviscosity and density; extruding the combined streams from the thirdzone through an orifice of predetermined size and shape; and conductingthe extruded streams under streamlined laminar flow conditions atcontrolled flow rates to a mold assembly to complete polymerizationand/or cure.

The steps of bringing together in a single zone the necessaryingredients and causing high intensity high shear mixing action toproduce a substantially homogeneous thixotropic low viscositypolymerizing mass which provides material for both the base coloredstream and differently colored stream are important in accomplishing theeventual equal matching of the degrees of polymerization of the thestreams and in maintaining high flow rates through the system. Thefollowing steps relating to the controlled addition and handling of thepigmented stream or streams are also important and significant so far asthis invention is concerned. As mentioned above, the initial mass ofpolymerizing material is divided into two streams, one of which isconducted under controlled predetermined conditions of temperature andpressure, and at predetermined flow rates into a second and third mixingzone. Of considerable significance and benefit is the improvementachieved Where as in Zone II a stream comprising differently coloredpigment usually minor in size, is combined preliminarily with the onestream of polymerizing material of base color and is intimately mixed toprovide at a later point (Zone III) a differently colored stream havingsubstantially the same degree of polymerization as the other stream ofbase colored polymerizing material moving directly from Zone I and whichdifferently colored stream is to be folded within the other stream inthe third low intensity mixing zone (Zone III). It has been found thatone preferred and practical Way of matching these P lymerization ratesis to divide the initially formed polymerizing mass into two streams andthen to divert one polymerizing stream to incorporate therein adifferent veining color and thereafter recombine the streams, the age,velocities, sizes, temperatures and other conditions of the separatedstreams being carefully controlled in a predetermined manner such thattheir degrees of polymerization and preferably their rates ofpolymerization, densities, and viscosities are substantially equallymatched when recombined. As the differently colored polymerizing streamor streams are folded into the other base colored polymerizing materialin Zone III they are progressively displaced therethrough in at leastone predetermined reproducible three-dimensional configuration with theintegrity and continuity of a colored stream substantially maintained.The recombined streams, While still flowable, are extruded as a singlestream through an orifice in the structure defining Zone III atpredetermined flow rates and under streamlined flow conditions prior toentering a mold assembly. The How rates, conditions and dimensions ofthe extruded material and its orifice are controlled so that theextruded composite stream comprises at least one differently coloredvein r stream, of polymerizing material with its integrity stillmaintained, distributed throughout the other base-colored polymerizingmaterial in a predetermined, repetitive, reproducible,three-dimensional, irregular pattern having predetermined colorrelationship to the other base colored polymerizing material.

The final step involves directing the flowable extruded composite veinedpolymerizing stream to a mold assembly in a predetermined controlledmanner, preferably under the control of suitable movement programmingdevices operated in accordance with stored control signals, andpermitting the material to undergo curing or solidification within alimited predetermined controlled time period.

The features and controls of the above-described process are directedtoward bringing together differently colored streams but otherwise ofsubstantially equally matched properties of a compatible resin systemwith low shear, low intensity mixing such that when placed in a moldassembly they will (I) maintain the individual color characteristics,and (2) undergo curing of substantially the same rate under the sametemperature conditions. It is therefore necessary, especially in Zones Iand II, to control pressure, temperature and degree of mixing such thatthe polymerizing system does not overheat in the case of exothermicreactions and does not become excessively viscous in the case ofthixotropic rapidly gelling resins. Since most commonly used resins,such as poly(methylmethacrylate) and polyester resins, form gels whichundergo a viscosity change with increased agitation, especially underhigh shear mixing characteristics, it is necessary to keep the zonescompletely filled. Therefore, the pressure in each zone and relatedconduits must be maintained high enough, to achieve fast flow throughthe system, such that cavitation and its resulting undesirable effectsof poor mixing and the formation of gas bubbles is not permitted tooccur. In the case of exothermic reactions it may be desirable totransfer heat to or from one or both of the polymerizing streams tocontrol its polymerization rate relative to the other stream to assistin achieving the condition of substantially equally matched degrees ofpolymerization when the streams are recombined. Flow rates must becontrolled such that the material moves through the high intensitydevice at a rate fast enough to prevent the formation of highly viscousmasses before the combined streams reach the extrusion point. Underpredetermined controlled conditions established in the preferred systemthe moving streams of thixotropic polymerizing materials maintain highflow velocity characteristics of a low viscosity liquid while passingthrough the device, and this makes possible good orifice control and theaccuracy of volumetric mixing at Zone III in addition to high throughputwith minimum pumping power.

As will be recognized by those skilled in the art the size of theapparatus and the relative sizes of the conduits, mixing zones,agitation blades, etc. are dependent upon the volume of product beingcast on a mold assembly in any given period of time. Within any one setof sizes or casting rates the apparatus will be controlled as to therelative sizes and dimensions interrelating Zones I, II and III andtheir cooperating conduits in a manner dictated by fluid dynamics andthe vein pattern desired in the final cast article.

In the process of this invention the viscosity of the polymerizingfilled basic colored material and the viscosity of the contrastingcolored pigment streams must be substantially equally matched withincertain limits in order to better control the structure and appearanceof the vein or colored vein pattern and properties of the cast articles.In the case of poly(methylmethacrylate) the base colored polymerizingstream and the differently colored stream, both of which containcatalysts, modifier, promoter and filler, are in the range of 30 to 75poises and preferably 44 to 64 poises at the time of mixing in Zone III.(Viscosities are measured with a standard Brookfield viscometer usingspindle No. LV4, at 60 r.p.m.)

The viscosity of the small stream comprising the differently coloredpigment which provide the contrasting color, which small stream isinjected into the second high intensity mixing zone, usually lies withinthe range of .9-3 poises but is not in itself critical to the invention.

It has been found desirable and feasible (1) to control the size of thedifferently colored streams, or veins in the final product by regulatingthe size and type of mixing paddles and/or agitator blades used in ZoneIII; (2) to control the size of the differently colored stream as itenters Zone III; (3) to control the depth and degree of shear in mixingthe differently colored stream with the basic stream and, (4) ifdesired, to further control the vein construction and direction duringthe filling of the mold assembly.

Additional colors in the form of additional small streams comprisingcolored pigments can be added to the base polymerizing material, eachsmall stream comprising different colored pigment added to a differenthigh intensity high shear mixing zone comparable to Zone II such asillustrated schematically in FIG. 7 as Zones Ila, b, c by dotted lineroutes having fed into each individual Zone a different color a, b, 0,etc. Of course, in such a modification of the apparatus and processseparate streams would be diverted from a high intensity mixing Zone Iinto the multiplicity of Zones IIa, b, and c, depending on the relativeintensity of each color to be recombined in Zone III. Each color must beadded through a separate second zone chamber having predeterminedconditions of size, temperature, pressure and agitation and flow, suchthat when all streams are combined in Zone III the polymerization ratesare substantially equally matched. The volume of the Zone IIcompartments must be carefully adjusted to maintain the desired resultsdiscussed for the single differently colored stream embodiment discussedabove.

In most cases the lowest possible degree of mixing is employed in ZoneIII. The differently colored stream is folded into the base coloredstream so that normally, considerably less than 5% blending takes placewithin the zone. In some cases a controlled slight degree of blending ordiffusion of the colored stream into the background polymerizationmaterial enhances the threedimensional vein pattern of appearance bycausing variation in the contrast between the veins or colored streamthan the other material. This contrast can be varied by changing thesize of the differently colored stream as it is injected into Zone III.Of course the intensity of color of the differently colored stream canbe controlled by the amount of coloring matter added at Zone II.

The desired differently colored stream or patterns are produced inmaterial cast on a molding assembly on a one scale by introducing thedifferently colored polymerizing stream into the base coloredpolymerizing stream at Zone III with a material displacing member havinga configuration that provides very low shear mixing action. The veinsare formed by directing one or more controlled streams of thedifferently colored polymerizing streams in diameters ranging from toinch or by folding large wider bands ranging from 1 to 2 inches, intothe base colored polymerizing material for controlled distances. Thedifferently colored streams or veins are formed in the base coloredpolymerizing stream by means of a number of low shear mixing bladeelements engaging the material in the third mixing zone and havingmaterial deflecting surfaces of predetermined size and configuration,Preferably, the mixing blade elements are mounted on a rotary member orstirring arm and range in width from to /2 inch. The rotary member inZone III used in the described embodiment of this invention is rotatedat speeds between 50 and 200 feet per minute. The axis of rotation ofthe rotary member is preferably maintained at an oblique angle to thegeneral direction of flow of the polymerizing material through the zone.In this arrangement, the mixing blade elements are adjusted such thatthe differently colored stream is folded into the base colored stream ofpolymerizable material in the low intensity mixing, Zone III, from theouter periphery of a mass towards its center by the mixing bladeelement. Usually the differently colored streams are folded or blendednear the outer periphery of the path of the turning blade element in thelow intensity mixing zone with the stirring arm turning at about '20 to500 revolutions per minute while the polymerizing material is passingthrough the zone at a rate of about .1 to 2 cubic feet per minute. Theamount of blending taking place may be regulated by the varyingrotational speed of the blade elements or by varying the rate of How ofthe polymerizing material through the low intensity mixing zone.Normally, for best results the throughput of the polymerizing materialthrough Zone III is adjusted such that at speeds of 122 feet per minuteof the blade element, the polymerizing material is extruded from ZoneIII through an orifice of inch to inch wide and thereafter is subjectedto laminar or stream line fiow conditions for a distance of /2 to inchesat velocities in the range of from 8 to 120 feet per minute prior toentering the mold assembly. This is necessary to maintain control overthe colored vein configurations. The material is preferably laiddirectly onto the mold surface with little roll-over or scatteringtaking place in the mold assembly. The apparatus for producing thearticles of the invention will be described in greater detail at a laterpoint in this specification.

For best results in filling mold assemblies, and in achievingreproducibility of patterns where the extruded stream from the thirdmixing zone is narrower than the mold assembly, a controllable presetprogramming means for controlling lay-down of the extruded stream in themold assembly is required as shown schematically in FIG. 6. Where thewidth of the extruded stream with its particular pattern corresponds tothe width of the mold assembly, a direct one pass lay-down of theextruded stream is the desired mold assembly filling technique. In theprior art where less control and a smaller degree of reproducibility wasaccepted, the lay-down of the extruded stream of polymerizing materialwas accomplished by manually programming the extruded stream of a givenWidth onto a wider mold assembly. In so doing, the directional characterof the individual separately identifiable streams of colored pigmentwithin the mass obviously was varied by the person applying the resin tothe mold assembly. In so doing, the pattern variation of the productcast on the mold assembly varied from one cast object to the next whichwas undesirable in mass production techniques where reproducibility andpattern matching are desired. In the development of such a pattern aperson would incorporate swirls, waves, and zigzags to his personalliking. However, it has been found that even when following specificdirections the pattern made by one person differs significantly from thenext and created problems for manufacturing at one time acceptablepatterns which can be blended or matched compatibly with other patternsproduced at some other time by other people. This is particularly truein the manufacture of large cast sheets or objects, for example, in therange of 3 feet by 8 feet for use in wall panels, wherein matching ofveins as to direction or configuration or other aspects is somewhat moreimportant than normally encountered with smaller panels or objects madeto resemble marble.

Another feature of the mold assembly filling operation is thearrangement required to achieve a clean, smooth, glossy finish on themajor use surface of the cast article. Usually the extruded stream ofpolymerizing material is laid down in a mold assembly which, preferably,comprises a fiat surface unit with sidewalls or raised side edges tocontain the cast material, the major use side of the cast article beingthat surface which is laid down in contact with the bottom of the moldassembly unit. In order to achieve a clean, smooth, glossy finish on thesurface of interest of the cast article, and prevent adherence to themold assembly, it has been found highly desirable to place a thindisposable film F of an organic polymeric composition on the flat moldsurface as shown in FIG. 1, such that the film is interposed between themold surface and the material being cast or laid down thereon. As taughtin prior filed US. application Ser. No. 834,985 filed July 23, 1969 inthe name of Billingsley et al., and assigned to the assignee of thepresent invention it is also highly desirable to place between the moldsurface and the film, a restraining fluid of controlled viscosity whichholds the polymeric film against the smooth mold surface whilepermitting lateral movement of the polymeric film during the shrinkingof the cast item. It is an important requirement that the shrinkageproperties of this film be substantially matched to the shrinkageproperties of the polymeric material placed thereon, especially on amoving mold assembly. Unless a lubricant-restraining fluid is added tothe surface of the mold prior to the laydown of the thin polymeric filmit is believed that the high degree of shrinkage of the polymerizingmass relative to the surface of a flat rigid mold assembly (usuallymetallic) causes wrinkling and undesirable surface irregularities on thefinal article. The type of lubricant selected is one which will notattack the film or the mold surface. Usually lubricating petroleum oilssuch as S.A.E.-1O are suitable for such films as polyethylene, polyvinylalcohol, cellophane, polyethylene terephthalate, polyvinyl acetateresins and others. It is preferred that the films be biaxiallyshrinkable under the action of heat or certain solvents and be ofuniform thickness in the range of .5 to about 30 mils. As an example ofthe shrinkage encountered, a 20%30% volume reduction occurs duringpolymerization of methylmethacrylate polymers. This decreases with theamount of filler present, of course, and a typical example, a 60% filledpoly(methylmethaciylate) system shrinks about .5 to 3 linear percent.The preferred film composition is one in which shrinkage nearly matchesthat of the polymer system.

In some instances it is also desirable to add a cover sheet ofdisposable polymeric film to the top of the polymerizing mass to preventvolatilization during curing processes. Such an arrangement ofdisposable film F indicated in FIG. 1 is shown being added continuouslyto the top of a continuous belt operation whereby the polymericcomposition is laid down on a film F and covered with film F The topcovering film should have properties similar to the bottom film, but,however, since the surface that it is in contact with is not necessarilythe primary use surface its shrinkage characteristics need not be ascritical.

Another important feature in manufacturing on a continuous large scaleis the revention of loss to the atmosphere of chemicals and reagentsinvolved in the polymerization. In organic polymerizing systems loss ofvolatile components such as monomer not only interfere with thecomposition of the final cured mass but also present a hazard to thepersonnel in the form of poisonous fumes, fire and/or explosion hazards.The use of an entirely enclosed mold such as demonstrated in the aboveparagraph whereby a top covering film is added to the molded resin or atwo-piece mold assembly can reduce these deficiencies.

In the continuous operation, however, where polymeric compositions areadded to the partially exposed mold assembly for long periods of time,there is bound to be contamination of the atmosphere by reactants in thesystem unless precautions are undertaken in addition to those alreadydiscussed. One solution is to provide blanket means to cover the exposedportion of the mold assembly with an inert gas which is lighter than thevapors and/ or noxious gases emanating from the polymerizing mass, butheavier than the surrounding air. One example of such a protective layeris carbon dioxide over a polymerizing mass of poly(methylmethacrylate).Usually the contaminant in such a system is the highly volatilemethylmethacrylate monomer which evaporates to the atmosphere and causessurface cooling as well as precipitation of polymer on the top surfaceof the cast item. This is known to the art as skinning and is highlyundesirable. The use of the carbon dioxide blanket prevents skinning byholding a monomer vapor concentration at the point of saturationimmediately above the cast surface. Of course,

to practice blanketing on a continuous process, an apparatus orspecialized assembly is required wherein an equilibrium depth ofblanketing gas or vapor is used to maintain the vapor equilibriumdesired. Such an apparatus is shown in FIGS. 1, 2 and 3 as it applies toa continuously moving casting surface. This apparatus and its operationwill be described later in further detail. Such an apparatus is equippedsuch that the blanket continually moves from one side at a point closeto the bottom of the assembly to the top on an opposing side where it isremoved. By passing the blanketing gas over the surface at a rate suchthat unnecessary turbulence is prevented, the amount of vapor, usuallymonomer vapor, which es capes to the atmosphere is held to a minimum.Any that is mixed with the heavier gas through normal physical mixing ofthe vapor with the gas is removed and is disposed of by suitably safeand noncontaminating techniques. Such gases as nitrogen, carbon dioxide,argon, and Freon can be used and passed through absorbing towers toremove organic monomers characteristic of the reaction polymer system,and thereafter recycled for reuse as blanketing material. In a preferredoperation the extruded veined material emanates from the Zone IIIorifice at a position within the protective gas layer. Obviously, theadvantage offered by such a system is that the extruded material can beadded to the flat mold assembly in an unrestricted manner. Either anindividual or a movement programming or controlling device can directthe orifice over the mold surface in a desired two dimensional laydownpattern. Furthermore, an operator can work with full visibility of thecasting operation directly above the open mold assembly for longcontinuous time periods without being affected physiologically bynoxious monomer vapor.

With respect to the materials used in the practice of this invention, itis required that the polymerizing media into which the veining pigmentsare co-mingled be cured to a degree of about 75% within a time period nogreater than about to minutes for continuous operations.

It is believed that the process and apparatus described herein can beapplied to any inorganic or organic polymerizing systems which gelwithin the above time limits. Many fast gelling systems can be used suchas acrylics, methacrylics, polyesters, polyamides, polyformaldehydes,etc., which can be formed in a manner such that gas evolution andshrinkage do not destroy the vein' structure and appearance. It is alsobelieved that the system could be employed in certain fast settinginorganic plasters and cements.

The particular preferred system employed in the process and apparatus ofthis invention utilizes poly(methylmethacrylate) filled with calciumcarbonate, or alumina and marbleized with a great variety of veiningpigments and colors.

The starting sirup for polymer-in-monomer solution may be prepared byany of the methods described in British Pat. No. 870,191 or US. Pat. No.3,154,600. Specifically, the sirup may be made 'by heating a smallamount of a polymeriztaion initiator in solution in the methacrylicester and in the presence of a chain transfer agent at a suitablepressure and temperature. Heating is continued until the solutionreaches a predetermined viscosity. Thereafter the hot solution isquenched by the addition of cold monomer containing a polymerizationinhibitor. More specifically, a sirup having a viscosity of 0.5-50poises at 25 C. can be produced from methylmethacrylate by heating themonomeric methylmethacrylate in a jacketed kettle at a temperature of50-150 C. under refluxing conditions. These conditions normally producean atactic polymer. Atmospheric pressure is used and the refluxingmaterial is stirred. Heating is conducted in the presence of a verysmall amount of initiator and from the 0.05-1.0 mole percent of a chaintransfer agent, such as the alkyl mercaptans and the mercaptansdescribed in US. Pat. No. 3,154,600. When a bulk viscosity in the rangeof 0.5-50 poises, which corresponds to an inherent viscosity of 025-10is attained, and the initiator content has been reduced substantially to0, that is, below 20 parts per million, the polymerization is stopped bycooling in any suitable manner. In the present invention it is preferredthat the final solution contain 10-35% by weight and preferably 25-35%of the methylmethacrylate polymer dissolved in the methylmethacrylatemonomer. The polymer has an inherent viscosity of from 0.25 to 1.0determined at 20 C. using a solution of 0.5 gram of the polymer per 100milliliters of chloroform in accordance with the method described in F.W. Billmeyer, Textbook of Polymer Chemistry, Interscience Publishing,Inc. (1957) page 128.

Highly filled polymeric marbleized articles produced according to theinvention comprise predominantly an inexpensive inert inorganic filler(usually in the range of 30-65% and as high as in some cases) heldtogether with a translucent polymeric material. Compatibility of fillerswith polymeric material will vary from one polymer system to another;therefore, the words inert or compatible must be linked to the polymersystem employed. Materials which are generally used as fillers are, forexample, TiO alumina, titanates, barium sulfate, calcium carbonate,white leads, lithopone, China clays, magnesite, mica, iron oxides,Spanish, Persian, American siennas, etc. Fillers range from very dark,in the case of iron oxides, to the very white, in the case of TiO Thecolor of the major stream may be referred to as the base color in amarble. That is, it is the background through which the veins run. Dyesand colored pigments can be homogeneously mixed with the light fillersto produce the desired color.

For special effects, fillers can comprise glass frits, beads, powders,fibers and/ or metallic, organic or inorganic fibers of varying size,shape or color and combinations of these.

In the preferred polymer system disclosed, the filler is added eitherbefore the gelation or polymerization starts. Usually, a dispersingagent is also introduced to insure a homogeneous mixture. Methods fordispersing fillers are well known in the art. One procedure for fillingmethylmethacrylate systems is as follows:

A methylmethacrylate polymer-in-monomer sirup produced under theprocesses described above containing 25% polymer and having a viscosityin the range of 20-24 poises is mixed using a blade 'mixer withanhydrous calcium carbonate of particle size in the range of 6-10microns being commercially available under the name of Non Fer Al, aprecipitated particulate calcium carbonate having low iron content isadded in quantities to the sirup ranging between 40 and 65%. To thesirup-filler mix is added a dispersing agent to the extent of 0.1% to 1%by weight of the filler present. For example, Zinc stearate is added inquantities comprising from .010.1% of the calcium carbonate. Polymermonomer sirup containing 30-70% calcium carbonate filler ranges inviscosity from 30-60 poises.

Although the above example indicates that only mild mixing conditionsare required in the presence of a surface active agent to disperse thefiller, it should be understood that any type of mixing suitable todisperse the filler evenly in the monomer polymer solutions can beemployed. It has been found, however, that the majority of theabove-mentioned fillers, including such fillers as glass, silica, andmetal particles, having diameters less than 10 microns, can be suitablydispersed by the above-described manner.

According to preferred practice of the invention the above-describedfilled sirup can be used most satisfactorily when the teachings of US.3,405,088 and 3,362,942 are followed in conjunction with thewater-promoted cure teaching of the R. B. Duggins application Ser. No.838,688 filed July 2, 1969, and assigned to the assignee of the presentinvention discussed in a following section of this specification. Asatisfactory catalyst to effect a suit- 1 I able cure with the materialsof this invention is the presence of 0.05-5 mole percent of a metal saltof a hemiperester of maleic acid having the following formula:

x is an integer that has a value of l or more up to and including thevalence of the metal; and R [13s a saturated tertiary alkyl radical,preferably tertiary utyl.

In a preferred process for making marbelized filled polymer employing acontinuous process in apparatus to be described in more detail later, itis important to have a polymer system which undergoes a very uniform andvery rapid cure within a period of 5 to 15 minutes under conditionswhich are uniformly reproducible from day to day. When the resin ispoly(methylmethacrylate) and prepared as described above a very uniformand rapid cure is achieved by the employment of controlled quantities ofparticular solvents described in detail in prior filed US. applicationS.N. 838,688 filed July 2, 1969 to R. B. Duggins, and assigned to theassignee of the present invention produces increased high rates ofpolymerization which are obtainable on a reproducible basis. In atypical formulation 32.8 parts of polymer-in-monomer sirup is mixed withdistilled water until a total content of 700 parts per million of wateris obtained. The water functions as a mutual solvent for water solublecatalysts as described by Duggins. With this is blended 61.8 parts ofdry calcium carbonate or alumina in a high shear mixing device at atemperature not exceeding 85 F. This mixture is blended under highintensity mixing conditions with known quantities of thickeners,promoters, chain transfer agents, and catalysts in concentrationsconsistent with the teachings of the previously cited patents andtreated in accordance with the teachings of this invention to form,under high intensity high shear mixing the initial polymerizing mass ofbasic color from which mass the two streams previously dsicussed areformed.

With respect to the preparation of the colored stream or veining pastes,the veins in marble may have a wide range of color. The coloring matterselected for these veins is commercially available from a wide varietyof sources and is obtained under a number of tradenames. Coloring matterthat is insoluble or only slightly soluble in monomer or mixtures ofmonomers is incorporated in the polymerizable mixture to impart veins'The term pigment as applied to such coloring matter is here used in thebroad sense of a powdered or powderable material which can be mixed withliquid to impart color thereto, including black and white. The term dyethus includes lakes, toners, and organic and inorganic pigments. Theterm pigment includes those that are opaque, translucent, andtransparent. Transparent pigments are those which impart color withoutopacifying and without being dissolved. Inorganic pigments may benatural or synthetic. They are usually metallic compounds. Typical ofthese are barium sulfate, titania zinc oxide, zinc sulfate, zirconiumoxide, various lead compounds, lithopone, etc. Also included are blackiron oxides; hydrated yellow oxide, venetian reds; cadmium yellows,oranges, reds, and maroons, including cadmium sulfoselenide, cadmiumyellows prepared with zinc sulfide or barium sulfate, cadmiumlithopones, or cadmium sulfoselenides; umbers;

12 metallic browns, such as calcium limonite or siderite; brown ironoxides; ochre; synthetic yellow or orange iron oxides; chrome yellows;antimony yellow; chrome greens; iron blues; cobalt violets; carbonblacks, including channel and furnace blacks; luminous andphosphorescent pigments, including special grades of zinc sulfide andactivating agents; leafy pigments giving pearlescent effects, such aspearl pigments; lead iodide; mercurious chloride; bismuth oxide; metalbronzing powders; aluminum powders; aluminum bronze; copper aluminumbronze powders; gold leaf; silver; copper; and nickel.

Organic pigments are included in a large number of classes. The organiccoloring matter differ considerably in light fastness and are selectednot only for the color or shade desired but for conditions which areencountered in the use of the pigmented plastics and in thepolymerization of the mixture. Thus, organic pigments are selected notonly for shade but also resistance to the possible action of theinitiator system. Conversely, the initiator system may be adapted to thepigment. In the case of organic colors which tend to be soluble in themonomer system, the color may be used in a lake.

The colored pigment or pigments to be added as veining materials shouldbe dispersed in monomer or sirup described previously to form a fluidfeed stock. Some pi gments can be worked, or milled, into monomerpolymer or mixtures of monomer and polymer without added dispersingagents. In other cases it may be desirable to utilize a dispersing agentto overcome agglomeration of pigment. Typical dispersing agents includelignin sulfonates, polymers of maleic anhydride, dodecyl sodium sulfate,etc.

Pigment may be mechanically mixed with monomer or monomers or with amonomer-polymer mixture or with simply a polymer. The resulting mixtureis then taken up in the rest of the monomer or monomer-polymer mixture.Milling of pigment may be done with a Wide variety of polymericmaterials which may be the same as, or different from, that to be usedin the monomer-polymer system. Any soluble acrylic polymer may be usedin this way. Likewise, pigment may be milled with a soluble styrenepolymer or copolymer. Vinyl chloride and/or acetate polymers may also beused and may be especially useful for dispersing carbon blacks.Cellulose acetate or cellulose acetate butyrate are also good media.Nitrocellulose is commonly used with carbon black and with dispersionsof phthalocyanine colors.

It may be desirable to grind or mill the pigments and colors in aplasticizer as well. A mixed plasticizing system of liquid monomer andpolymer is quite effective in dispersing the various pigments and theresulting paste is readily co-mingled with a filled monomer-polymersystem. A number of typical feed stock mixtures of pigment in polymethylmethacrylate polymer-in-monomer sirup are shown in Table 1.

Filled polymerizing organic polymer sirups containing initiators,catalysts, modifiers and base colored fillers, such as calciumcarbonate, iron blacks, etc., are made into articles having anappearance and structure pleasingly similar to marble by adding limitedquantities of one or more contrasting colored pigments dispersed in thepolymerizing base system. The description and disclosure of theinvention deal primarily with poly(methylmethacrylate) sirups, but areconsidered to have application to other polymer systems. The differentlycolored polymerizing streams which are used to simulate veins must becarried into the base colored polymerizing stream by means of mixingdevices operating under conditions which produce a desired low degree ofshear, with an extremely low degree of mixing in the polymerizing bulk.Pleasingly varied veins can be produced by conducting the combinedstreams through an orifice under streamlined flow conditions prior tofilling the mold.

The preferred apparatus embodying principles of this invention are shownin the FIGS. 1 through 5, In these figures are shown a manufacturingarrangement embodying a polished stainless steel endless conveyor 60*having the dimensions of 3 feet in width and a smooth flat castingsurface of approximately 100 feet in length. In cooperative arrangementwith this belt is shown a three-zoned, blending mixing and casting headdevice B haaving a first and second zone wherein high intensity, highshear mixing of polymerizing ingredients takes place and a third zonewherein low intensity, low shear blending takes place wherein thecolored veins are added to the base polymerizing stream to form thepatterned vein structure which is extruded and cast onto the moving beltsurface in a direction predetermined by mechanical and programmingmeans. Cooperating with this moving conveyor belt in the vicinity of thefilling location are means for feeding a continuous film F onto thesurface of the :belt as well as means for covering the freshly castmaterial with a cover film FT. In addition, an apparatus arrangement forblanketing the casting area with an inert gas is shown in FIGS.

FIG. 4 shows in detail the before-mentioned three zoned mixing andcasting head device B having a movable support element 1 with a verticalextending passageway 2 extending through it. The pasageway 2 cooperateswith portion 4 of casing element 5 to rotatably support the mainapparatus elements of the invention. As shown, elements 5, 6, and 7 forma composite housing assembly for high intensity mixing Zones I and II inwhich the polymerizable ingredients or materials are brought togetherand intimately mixed with high shear mixing action. A lower transverseplate element 17 comprising a gasketed flanged assembly, together withan interior cavity in element 7, form the chamber 19, for receiving andthoroughly, intimately mixing with a high intensity, high shear mixingaction the catalyzed filled polymer resin containing the base coloringand filling ingredient which is supplied from a storage tank (not shown)through metering devices (not shown) through flexible conduits 30 and30a into a base transverse element 8. An upper transverse plate element15 comprising a gasketed flanged assembly, together with an interiorcavity in element 6 form a second mixing zone, or chamber 13, in thecomposite housing assembly for receiving and thoroughly intimatelymixing with a high intensity, high shear mixing action in the confinedsecond zone having predetermined dimensions under controlledpredetermined conditions, a predetermined portion of the mixedingredients passing from the first mixing zone and a predeterminedquantity of coloring material entering from conduit 14 having a colordifferent from that of the mixed ingredients of the first mixing zone. Avertically extending, rotatably mounted shaft 9 extends through elements5, 6, and 7 of the composite housing assembly and is drivingly connectedat its upper end by means of a sleeve coupling element 10 to a flexiblerotary output shaft H of a variable speed electric motor 11 which issecured in operative position to the conveyor belt frame assembly. Thelower end of shaft 9 extends through the lower chamber 19, but isunsupported at the lower end. Orifice 17a formed in transverse element17 controls movement of a predetermined portion of the mixed ingredientsfrom the first zone to the second zone. By regulating the dimensions ofthe orifice 17a in a predetermined manner the desired portion of themixed ingredients of the first zone is permitted to move into the secondmixing zone. Rectangular blades 29 and 28 with square cross sections forhigh shear mixing are secured to the shaft 9 for rotary movementtherewith in the upper chamber 13 and lower chamber 19. Stability ofrotation of shaft 9 is enforced through stabilizing collar 23 andbearings 22 at the uppermost end of the shaft. Transverse element 15cooperates with a stationary plastic lubricating and sealing collar 16-'which is provided with passages to allow for flow of suitablelubrication fluids through interconnection with a conduit 18 and slotconduit 20 in the collar 16, which is held in cooperative arrangement byset screws S protruding through element 5.

The previously described component of the mixing and casting assembly Bcomprising Zones I and II is rigidly interconnected with the componentof the mixing and casting assembly B labeled Zone III in FIG. 4 throughconduit elements 31 and 34 and are joined at a longitudinal junctionplate assembly comprising flanges 35 and 36. Cylindrical casing element42 cooperates to form with transverse elements 41 and 44 on the upperend and with 43 and 45 and 46 on the lower end, a third low intensity,low shear mixing zone having predetermined dimensions. Conduit 31 is ofpredetermined dimensions operatively connected with the second and thirdmixing zones such that at a predetermined flow rate, and underpredetermined conditions, the stream of the intimately mixed differentlycolored material can pass from the second to the third mixing zone.Conduit 34 is operatively connected With the first mixing zone and thethird mixing zone and of predetermined dimensions for conducting, at apredetermined flow rate and under predetermined conditions, a stream ofthe intimately mixed ingredients from the first mixing zone to the thirdmixing zone. A vertically extending, rotatably mounted shaft 47 extendsthrough elements 41, 44, 42, 43 of the composite housing assembly ofZone III and is drivingly connected at its upper end by means for asleeve element 49 to a rotary output shaft 50 of a variable speedpneumatic motor 52 having an air inlet conduit 53. The motor assembly isfurther rigidly mounted to element 41 via coupling 51. Since the lowerend of the shaft which passes through cavity 40 is not rigidly fixed toa bearing, it is stabilized by a Teflon plastic sleeve supporting andseal element 44 which is positionally stabilized with set screws (notshown) which protrude through element 42 and lubricated by means similarto element 16. Longitudinal blade mixing elements 48 are secured to theshaft 47 for rotary movement Within the lower chamber 40 and act as amovable material displacing member having a predetermined size,dimension, and configuration constructed and arranged to providepredetermined, reproducible, repetitive movement at predetermlned ratesto produce a limited low intensity, low order, loW shear mixing actionon the combined streams of intimately mixed ingredients conducted fromthe first and second mixing zones and to displace the streams ofdifierently colored ingredients from the second mixing zones through theother streams. The shaft 47 is rotated under predetermined controlledspeed such that the differently colored stream 32 passes into the basecolored stream 33 Without intimate mixing, in at least onepredetermined, continuous, reproducible, separately identifiable,three-dimensional configuration. Orifice member 46, shown in greaterdetail in FIG. 5 by means of an end view at line 5-5 of FIG. 4, providesa restricted orifice of predetermined shape and dimension and acts incommunication with the third mixing zone to form a sheet comprised ofthe combined streams of polymerizing material. The shape of the orificenozzle 46 is easily removed and changed to other suitable assemblies andshapes by means of a threaded coupling 45 and represents only onepreferred form of the orifice.

It should be understood, however, that to operate the describedapparatus means must be employed to provide a driving force or pressureon the fluids moving through the apparatus. The preferred method is topump the liquid starting materials from their storage reservoirs usingstandard rotary or positive displacement pumps to provide the neededpressures in the first, second and third zones, and the conduits 32 and33. The pressures in the high intensity mixing zone can be furtherregulated by the incorporation of an orifice plate in either or both ofthe conduits 32 and 33 with orifices 39 and 38 to control the relativeflow rates of the streams conducted therethrough. Furthermore, toprovide additional control over the action taking place within the firstand second mixing zone, and related conduits, such that the materials ofthe streams passing into Zone III are substantially equally matched asto density, degree of polymerization, and viscosity it may be desirableto have heat transfer means cooperating with at least one of the highintensity mixing zones. Such a heat transfer means is provided by jacket24 providing a cavity 25 such that cooling or heating fiuids may bepassed into the zone by inlet 26 and removed through outlet 27.

The mixing and casting head assembly, comprising Zones I, II and III, isparticularly useful when applied on a continuous basis to lay downveined material in the manufacture of large sheets or slab-like objectsof a mableized product suitable for use in the building industry. Suchsheets normally are cut to lengths varying from 4 to 12 feet, havingwidths ranging from 2 to 4 feet. Preferred apparatus for casting such amarbleized product is shown in FIGS. 1, 2 and 3.

TABLE I Color designation Parts by weight;

Mixture:

A Brown 10 Parts raw umber 90 B Malaco blaek. {g, f 95 25 Light chromeGree G Olive green. 2 Dark chrome green 500 2 Lamp black 9 T102 1 DShell pink 9 Venetian red" 500 08 Bulletin red... E Talisman 0.5 Lampblack... 500

brown. 2. Raw umber. 3 'IiOz 2 F Florentine grey 2 Iron blaclL 500 0. 5Yellow ochel TiOz 4 Raw sienna. G Persian gold 1 Burnt umber. 500

1 .25 Raw umber." Venetian red- II Chinese red.

l Dispersed in 3 parts sirup. 2 1 part/3 parts sirup.

In FIGS. 1, 2 and 3 is shown an endless stainless steel belt havingdimensions 3 feet in width by about 200 feet in length with a thicknessapproximately 7 of an inch. This belt is stretched at high tensionbetween two drums (one shown) 61 mounted on trunnions (not shown). Ateach edge of the fiat belt is mounted endless siderails 62a and 62bwhich act to form the sides of an endles mold cavity having a totalflat, horizontal, usable surface measuring about 100 feet in length by36 inches in width. Additional supporting rollers are provided betweenthe rotating drums 61 at strategic locations. For best results, the topsurface of the belt upon which the resin is cast is maintainedcompletely flat and level. The belt is driven by an electric motorgeared to one of the major drums 61 (one not shown) at speeds rangingfrom /2 to 9 feet per minute. The casting surface is also furtherprovided with cooperating insulating and heating facilities (not shown)to maintain a fast cure rate and, finally, a cooling faciltiy (notshown) to remove heat from the cast sheet such that safe manual handlingcan be accomplished. In accordance with the teachings of prior-filed US.patent application Ser. No. 843,985 filed July 23, 1969 in the names ofBillingsley et al. and assigned to the assignee of the presentinvention, the highly polished surface of the stainless belt is lightlycoated with a restraining liquid through a distributor manifold 63 and asqueegee-type spreader 64 to regulate the amount of liquid added to thesurf-ace. A releasing film F of polyvinyl alcohol resin having athickness of 1 /2 to A2 mils is fed continuously from a roll 65 andplaced against the smooth casting surface. The film release sheet F ispressed into intimate contact with the stainless belt by roller 66pressing against the belt pulley 61. A frame structure comprisingupright sections 67 and 68 is located adjacent each side of the belt andis interconnected directly above the belt by transverse sections 69. Theupright and transverse sections are constructed as shown in FIGS. 1, 2and 3 from angles, channels and I-beams of suitable thickness andstrength to support the mixing and casting assembly B of FIGS. 4 and 5,as well as mechanical controlled drive mechanisms for said apparatus.The mixing and casting assembly B is carried by a traveling beam 70which moves in a plane parallel to that of the casting belt. The beam 70rests on roller bearings 73 which permit longitudinal slidingarrangement of the beam in a direction parallel to the movement of thebelt. These bearings are supported in a transversely movable carriage 71mounted on four wheels 72 which ride in opposed transverse channeledportions of the transverse sections on members 69 parallel with the beltsurface in a direction at 90 to the direction of travel for the belt.The carriage 70 is moved transversely to the direction of the belt bymeans of cables 74 attached thereto and cooperating with guide pulleys75 mounted in the frame structure as shown. At one side of the belt thecable is moved in one direction by a suitable power drive arrangement 76and is moved in the other direction by a similar power drive arrangement76a. The alternating back and forth motion is controlled by a hydraulictrip valve switching arrangement which is actuated at the end ofcarriage movement in one direction to activate the other drivearrangement. This same bydraulic trip valve arrangement also acts at thesame time to activate a reciprocating hydraulic piston unit 88, whichadjusts the angle of the pivotally mounted guide rail beam 81 which ispivotally mounted at 81F. Guide rail beam 81 is provided with linear camrails 100 which cooperate with cam rollers 101 carried by beam 70 tocontrol its longitudinal position relative to the carriage 71. Thecooperation of rollers 101 with rails 100 during transverse movement ofcarriage 71 carrying the beam 70 controls the angle of travel of themixing and casting head B across the casting surface of the moving belt60. In order to maintain the same resultant angle or basic track ofmaterial cast across the moving belt during movement of the mixing andcasting head B across the belt, the guide rail beam is adjusted bypiston unit between two predetermined positions, one for each directionof movement of the head B across the belt. This adjustment issynchronized with the back and forth movement of head B and carriage 71by means of the trip valve arrangement described previously. A hydraulicmaster piston motor 79 actuates slave piston motor 80 which is connectedas shown in FIG. 1 to a bracket 104 secured to beam 70 and which carriescam rollers 101 which travel along the guide rails on the guide railbeam 81. Motor 79 comprises a piston 79a which responds to movementcaused by its engagement .with the surface of cam 78 which rotates atspeeds pre-controlled by adjusting its cooperating variable speed drivemotor 77. By adjusting the speed of motor 77, the shape of cam 78 inthis arrangement, a predetermined irregular movement can be superimposedon the basic diagonal movement of head B back and forth across the belt.The shape of cam 78, the speed of motor 77, the rate of transverse ofcarriage 71 can be coordinated in a predetermined controlled manner toprovide a programming means cooperating with the mold assembly speed tocontrol the path of the orifice 46 of head B as it moves the extrudedstream across the molding assembly in a predetermined, reproduciblepattern under controlled, non-turbulent flow conditions. The rate ofpolymer addition to the belt is integrated with the speed of the forwardmotion of the belt surface and the polymer storage pumping devices. Asthe resin is placed onto the casting surface it moves forward and passesunder a gauging plate 82 which can be adjusted at the thickness desiredwhen the resin is squeezed between the film covered belt supported byroller 83 and the covering film F passing between the gauge plate andthe top surface of the polymerizing resin. Independently supported onthe upright portions of the frame structure is a means for gasblanketing the molding assembly and the stream of castable polymerizingmaterial moving from orifice 46 to the mold assembly. and which isarranged to maintain a continuous moving protective blanket of an inertgas between the surface of the polymerizing material on the surface ofthe mold assembly and the surrounding atmosphere for a predeterminedtime period or until the castable material is covered by the coveringfilm F The gas blanketing means comprises a box arrangement havingvertical sides 84 and horizontal bottom elements 85 which slidinglyengage the side rails 62 to form a seal, the remaining side of the boxarrangement is formed by the moving film F One side of the box isprovided with a gas inlet manifold 86 which fills the box through aseries of branch connections 86a with a heavy inert gas to a point abovethe nozzle tip at Zone III of the veining head. Gas, as it passes fromone side of the belt to the other, is withdrawn by a series of outlets87a which are connected to the outlet manifold 87 at the opposing sideof the casting assembly. The gas is then discharged to disposal devices(not shown).

In a preferred apparatus arrangement embodying principles of theinvention and suitable for producing rectangular thin inch, 2 inchesthick) cast articles in large sheets, the following specific informationis given:

Conduits 14 and 30, 30a which supply materials to chambers 13 and 19from storage tanks are .-inch flexible and flt-inch flexible tubingconnecting with pumping devices used to meter accurate quantities ofmaterials to the moving blending head device. With 60% calcium carbonatefilled poly(methylmethacrylate) resin containing pre-controlled amountsof catalyst chain transfer agent and, in some cases, release agents, apositive displacement gear pump is used to transfer 16.7 lbs. per minuteof material having a specific gravity of 1.6 into the lower chamber 19through line 30. An accelerator is added at 30a. The lower chamber isabout 2-3 inches in diameter and about 4 inches in height. Thepolymerizing ingredient passing through chamber 19 is mixed by the highintensity blades 29 rotating at speeds approximately 600 to 3000 r.p.m.Each blade section is made in a square high shear configuration having 7inch on a side. This thixotropic mixture is then forced out of chamber19 by the pump into the %-1I1Ch pipe conduit 34 and also into thechamber 13 through the -inch opening 17a surrounding the shaft 9 intransverse section 17. The ratio of material passing into the A-inchpipe conduit 34 through longitudinal section 37 to that material whichpasses into chamber 13 and out through conduit 32 into the /z-inchtransverse opening 39 and into chamber 40 is regulated by the adjustmentof the conduit elements 31 and 33 size ratio, as well as the size ratioof orifices 39 and 38. At the above rate this amounts to about 20%through orifice 39 and about 80% through a /s-inch orifice at 38. Thecoloring matter entering through flexible line conduit 14 and theentering base mix in chamber 13, which measures l-2 inches in diameterand 2-3 inches in length, is further subjected to high intensity, highshear agitation to form a uniformly colored effluent and is preferablycooled to remove some of the heat of exotherm. At this point thereaction rate can go beyond that passing into conduit opening 34 due tothe additional mixing. Water at 17 to 20 C. is passed into the coolingchamber 25 at inlet 26 and exits at 27. The cooling media also acts toprevent overheating at the bearing surfaces at the collar 16 which canbe lubricated by forcing oil in conduit 18 through the sleeve opening 20and around the circumferential chamber of sleeve 16. The lubricant alsoserves as a sealing means around the rotating shaft which is inspectedthrough sight port opening 21 where excess lubricant can be discharged.It is important that no air be sucked into the turbulent mixingassembly, since air pockets formed in the fast polymerizing resin showup in the cast article as bubbles. A colored pigment stream is pumped inthrough a metering device at inlet 14 into chamber 23 at a rate ofapproximately 9 grams per minute of slurry containing 25% pigment. Thecoloring pigments are blended at the rotation of high shear mixingblades 28 which are constructed of square steel keystock as describedfor blades 29. The colored stream is then co-mixed with the base streamin desired volume proportions in chamber 40 which is approximately l-2inches in diameter by 3 inches deep. The shaft 47 is rotated by apneumatic motor at a rate of about 200 r.p.m. and blends the coloringstream into the base color using rotating low shear blades 48 having athickness of inch and a width of about A inch. The veined material thenpasses out of an orifice having a width of about 1 /2 inches and anopening of about inch at 46 and passes onto the moving casting surfaceat a specific gravity of 1.6. When the belt surface moves at a rate of 3feet per minute the laydown rate just stated is sufficient to form asheet 3 feet wide at a thickness of approximately 4 inch. As the castinghead traverses across the belt at an angle approximately 45 to thedirection of travel the streamline flow from the nozzle lays down aresultant pattern formed by a relatively linear basic direction with anirregular transverse oscillating movement superimposed thereon byoperation of the cam operating device at 78 and hydraulic cylinder 81.The carriage movement is regulated such that it traverses across thebelt surface and back at about 20-second intervals.

In the operation of the mixing and casting assembly in head B definingZones 1, II and III, it is to be understood that the volume ratio ofmaterial passing from Zone II to the material passing from Zone I can bevaried while maintaining the polymerization rates and degree ofpolymerization essentially constant and substantially equal at theirpoint of entry into Zone III. Several things can be done to maintainthis degree of constancy, especially with thixotropic fluids undergoingpolymerization at a rapid rate, which are: to vary the heating andcooling rates of the material in Zones I and II, to vary the volumetricsize ratios of Zones I and II and their outlet conduits 31 and 33, aswell as the regulation of the relative sizes of the orifices 39 and 38.It is contemplated that the major portion of material entering Zone 111could be the differently colored stream emanating from Zone II, whichcould be constructed to provide larger volume than Zone I. Therefore,the coloring of the veining pattern previously described wouldessentially be reversed in that the base colored stream would create thevein structure.

Especially under continuous operating conditions as describedpreviously, the vein pattern structure and appearance at a given pointis reproducible and will be substantially repeated by the apparatus overcontrollable periods of time to make possible closely matching patternsproduced in large sheets of cast material. When the extruded stream isnarrower than the mold assembly such as described in the apparatus inthe FIGS. 4, 5 and 8, additional predetermined and reproduciblevariations in the vein pattern of the final article can be controlled byachieving the laydown pattern of the stream in the mold by thecontrollable movement programming arrangement. A schematic showing ofsuch an arrangement is shown in FIG. 6, in which is indicated amechanically controlled device described in more detail in FIGS. 1, 2and 3. The type of laydown pattern which such a device yields isindicated in a plan view. The irregularity of the laydown path isdictated by the shape of cam 78 and the speed of motor 77 which drivesit.

While the previous discussion, in detail, relates to a preferred form ofapparatus described specifically in FIGS. 1 through 5, it is pointed outthat alternate forms of apparatus within the scope of the invention, aresuitable to carry out the process discussed. Various alternatives havebeen provided for that component of the mixing and casting head whichestablishes the low intensity, low shear blending Zone III. Suchalternative apparatus designs are shown in FIGS. 8a, 8b, 8c and 8d andhave 19 certain advantages in handling higher rates of flow of materialthrough the system. These figures show apparatus components which can beincorporated with the component defining high intensity Zones I and IIof the previous figures and used in placed of the component definingZone III indicated in FIGS. 4 and 5. FIG. 8a shows a low shear, lowintensity mixing zone comprising a cylindrical chamber 140 having anoverflow weir out et 145 which empties into an elongated, rectangularshaped conduit 146. Rotating within the elongated cylindrical chamber140 is a six-bladed 141 folding paddle rotated in the direction shown bythe motor driven shaft 150. The blending device is adapted to fit theoutlets of the high intensity mixing device indicated in FIG. 4 atconduit openings 38 and 39. Since the chamber 140 empties by a flowagainst gravity, it is provided with a drain plug 144, such that therapidly polymerizing material can be quickly drained and cleaned toprevent a freeze-up of the rotating blade mechanisms on shutdown of thesystem. As the mixing device is rotated in the direction shown, thethree low shear blades mounted at the left on angled members 142 and 143force the polymerizing mixture towards the periphery of the cylindricalchamber while the three blades on the right force the resin toward thecentral portion of the cylinder. The members 142 and 143 are angled suchthat they act as propellers to drive the resin toward the uppermostportion of the chamber where it will pass through the outlet 145 andmove under streamlined conditions through conduit 146 as it passes ontothe mold assembly. Another modification of this device is shown in FIG.811 wherein the six-blade propellered blending mechanism is replaced bya rotating auger or screw member 241 mounted on shaft 250. The pitch ofeach blade 248 on the auger is adjusted such that when rotated in thedirection shown the colored material is folded and cut into the basecolored mass and is moved towards the uppermost section of the chamber240 where it passes through opening 245 and moves through rectangularshaped conduit 246. Upon the shutdown of the apparatus it also can bedrained by removing plug 244. FIGS. 80 and 8d indicate another apparatusfor low intensity, low shear mixing which employs the features of 8a and8b in combination to a certain degree. The blending chamber 340 iscomposed of an elongated narrow, vertical cylinder which is centrallypositioned above a wider cylindrical area. Onto the shaft 350 passingthrough the center of each cylindrical area is mounted an auger or screwdevice 341 having blades which are pitched in a direction to force thepolymerizing mix into the lower portion of the chamber, wherein it isrotated by the sixbladed paddle device 341 mounted between propellerlikemembers 342 and 343. When rotated in the direction shown in FIG. 80, thecombined apparatus acts to force the polymerizing mixture from theuppermost end of the chamber towards the bottom end of the chamber withprecontrolled speed and blending, and thereafter through an elongatedflattened exit on extrusion passageway 346, as shown in detail in FIG.8d. The passageway 346 is formed by spaced opposed parallel wallportions 348 and 348a cooperating with opposed wall plate elements 347and 347a, the elements 347 and 347a held in position by suitable bolts349. While the above-described components of FIGS. 8a, b, and c havebeen provided as alternate designs useful in creating veined structuresin a polymerizing mass, the intermediate products formed thereby havingseparately identifiable distinct veins, which are slightly different inaesthetic character from one another. The alternative designs do notnecessarily produce exactly the same veined pattern in a polymerizingmass being cast.

It is believed to be clear from the foregoing description and discussionthat a novel improved intermediate product and production arrangementtherefor has been provided in accordance with the objects of theinvention.

Although certain preferred embodiments of the invention have beendescribed in detail in accordance with the Patent law, manymodifications and variations within the spirit of the invention willoccur to those skilled in the art and such are considered to fall withinthe scope of the following claims.

What is claimed is:

1. An improved high speed apparatus for continuously producing anextruded fiowable, castable stream of colored rapidly polymerizingmaterial in predetermined dimensions, said stream having distributed andsuspended therein at least one relatively smaller elongatedsubstantially continuous, coherent independent separately identifiable,compatible mass of differently colored rapidly polymerizing thixotropicmaterial disposed in a predetermined repetitive reproducible irregularthree dimensional pattern the differently colored polymerizing materialsbeing substantially equally matched as to viscosity, density and degreeof polymerization, said apparatus comprising in combination, a firstmeans for receiving and bringing together and thoroughly intimatelymixing with a high intensity high shear mixing action in a confinedfirst mixing zone of predetermined dimensions under controlledpredetermined conditions, predetermined quantities of a plurality ofpolymerizable ingredients, a second means for receiving and thoroughlyintimately mixing with a high intensity high shear mixing action in aconfined second mixing zone of predetermined dimensions under controlledpredeterrnined conditions a predetermined portion of the mixedingredients from the first mixing zone and a predetermined quantity ofcoloring material having a color different from that of the mixedingredients of the first mixing zone, a third means of predetermineddimensions operatively associated with said first and second mixingzones to control movement of a predetermined portion of the mixedingredients of the first zone to the second mixing zone, a fourth meansdefining a third low intensity, low shear mixing zone of predetermineddimension, a fifth means of predetermined dimensions operativelyconnected with said second means and said fourth means for conducting,at a predetermined flow rate and under predetermined conditions a streamof the intimately mixed ingredients of different color from said secondmixing zone to said third mixing zone, a sixth means of predetermineddimensions operatively connected with said first means and said fourthmeans for conducting, at a predetermined flow rate and predeterminedconditions a stream of the intimately mixed ingredients from said firstmixing zone to said third mixing zone, a seventh means cooperating withsaid fourth means and comprising a movable material displacing member ofpredetermined size, dimensions, and configuration constructed andarranged for predetermined, reproducible, repetitive movement atpredetermined rates in said third mixing zone to produce a limited lowintensity low order, low shear, mixing action on the combined streams ofintimately mixed ingredients conducted from the second and third mixingzones and to displace the stream of differently colored ingredients fromthe second mixing zone throughout the other stream, without intimatemixing, in at least one predetermined, continuous, reproducible,separately identifiable three dimensional configuration, and seventhmeans further comprising a driving means operatively connected with saidmaterial displacing member for moving said member in said third mixingzone, said fourth means further provided with structure defining arestricted orifice of predetermined shape and dimensions incommunication with said third mixing zone to form a sheet comprised ofthe combined streams of polymerizing material, eighth means cooperatingwith said first, second, fourth, and fifth means for developing in saidstreams a predetermined level of pressure, said predetermineddimensions, conditions, and rates all controlled and predetermined suchthat a sheet formed by said restricted orifice comprises thepolymerizing material with the discrete differently colored stream,distributed therethrough in at least one predetermined repetitivereproducible three dimensional irregular separately identifiable patternand color relationship and such that such said streams are maintained inflowable condition at least until they pass said orifice, and such thatthe materials of the streams forming the extruded sheet aresubstantially equally matched as to density, degree of polymerization,and viscosity.

2. The improved apparatus of claim 1 which further comprises heattransfer means cooperating with at least one of the streams ofpolymerizing materials to assist in controlling the degree ofpolymerization thereof.

3. The improved apparatus of claim 1 in which said fifth and sixth meansare provided with means for controlling the relative flow rates of thestreams conducte thereby.

4. The improved apparatus of claim 1 which further comprises a movablehigh speed high shear material displacing and mixing members ofpredetermined size dimensions and configuration operatively mounted ineach of said first and second mixing Zones, and a high speed drive meansoperatively connected with said high shear material displacing andmixing members and constructed and arranged to drive said high shearmembers at predetermined velocity sufiicient to achieve intimate rapidmixing and maintain the viscosity of rapidly polymerizing thixotropicmaterials treated thereby at a low level for high velocity flow throughthe apparatus.

5. The improved apparatus of claim 1 which is provided with a ninthmeans cooperating with said structure defining said orifice, a moldingassembly and a stream of castable polymerizing material moving from saidorifice to said molding assembly said ninth means constructed andarranged to maintain a continuous moving protective blanket of an inertgas between the surface of said stream and the surrounding atmospherefor a predetermined time after said stream leaves said orifice.

6. The improved apparatus of claim 5 in which said ninth means comprisesa substantially horizontal opentopped enclosure assembly ofpredetermined dimensions cooperating with a mold assembly and saidorifice, said enclosure assembly constructed and arranged to maintain alayer of a gas heavier than air in position surrounding a stream ofcastable polymerizing material moving from said orifice to mold assemblyand overlying a portion of the material after it has been cast on themold assembly, such material comprising a volatile monomer component anda polymer component in a liquid or semi-liquid condition, said enclosureassembly comprising inlet means for supplying to said enclosure assemblypredetermined quantities of an inert gas heavier than air and outletmeans for removing from the enclosure assembly the inert gas togetherwith a certain amount of the volatilized monomer component, the rate offlow of said inert gas, the amount of volatilized monomer componentremoved, and the positions of the inlet and outlet means selected suchthat for the dimensions of said enclosure assembly and the amount ofpolymerizing material present therein, an intermediate layer ofsufiicient size and concentration of the volatilized monomer componentis maintained between the inert gas layer and the surface of the castmate rial to establish a substantial equilibrium condition between themonomer in the intermediate layer and mono mer in the cast material inorder to significantly limit additional escape of the volatile monomercomponent from the cast material and also limit formation of a polymerskin layer thereon.

7. The improved apparatus of claim 1 which further comprises aprogramming means cooperating with a molding assembly and said structuredefining said orifice for directing the extruded stream to the moldingassembly in a predetermined reproducible pattern and under controllednon-turbulent flow conditions.

8. The improved apparatus of claim 7 in which said programming meanscomprising an actuating means operatively connected to move said orificerelative to a mold assembly in accordance with predetermined controlsignals.

References Cited UNITED STATES PATENTS 2,816,741 12/1957 Shulfman 184X3,040,381 6/1962 Pioch 184X 3,081,487 3/1963 Hetfner et al 18-43,164,863 1/1965 Hunt.

I. SPENCER OVERHOLSER, Primary Examiner R, L. SPICER, JR., AssistantExaminer

